Optimizing the protective capabilities of helmets is one of several methods of reducing brain injury risk in sports. Football is often the focal point of concussion research because of its popularity and the high incidence of concussions associated with it. However, the rate of concussion is higher in ice hockey. Moreover, it is the most common injury for women's collegiate ice hockey, and the second most common for men's. The current helmet safety standards for hockey helmets have changed little over the past 50 years. The first hockey helmet standards were instituted by the Swedish Ice Hockey Association (SIA) in 1962. Shortly thereafter, US and Canadian organizations developed similar standards. Today, most hockey helmets bear stickers representing certification by 3 different organizations: the Hockey Equipment Certification Council (HECC), the Canadian Standards Association (CSA), and the International Organization for Standardization (ISO) represented by a CE marking. These standards all have similar pass/fail criteria that were implemented to reduce the risk of catastrophic head injuries.
Recently, concussion has gained national attention and become a research priority as the incidence of injury rises and concerns about the long-term effects of repeated mild injury are brought to light. Many strategies have been employed in attempts to decrease the incidence of concussion, such as rule changes, education programs, legislation, and improvements in protective equipment. Examples of rule changes designed to reduce injuries include fair-play and body-checking rules, which are implemented in some ice hockey leagues. Studies have shown a reduction in the incidence of more serious injuries including concussions when these rules are in place.
Education programs such as the Centers for Disease Control and Prevention's “HEADS UP” on concussion initiative and the Hockey Concussion Education Project (HCEP) were developed to help educate coaches, players, and their parents on preventing, identifying, and responding appropriately to concussions. Although most states in the US now have concussion laws in place, it is unclear at this time how effective they are. These laws usually focus on education, removal from play, and approval required for return to play.
There is currently no objective information available to consumers on which hockey helmets provide better protection against serious, as well as milder, head injuries like concussions. Prior to the development of the Football Summation of Tests for the Analysis of Risk (STAR) Evaluation System in 2011, this information was not available for football helmets either. Since the first set of helmet ratings using this evaluation system was released, the number of helmets receiving the highest rating possible of 5 stars has risen from just one to a total of 12 helmets in 2014. In the past, there were no conclusive studies on the effectiveness of different helmet types in reducing concussions on the field. However, recent research has demonstrated that the risk of concussion on the field is lowered with a helmet that better reduces head accelerations upon impact.
Football STAR was developed based on two fundamental principles. The first is that the tests performed are weighted based on how frequently a similar impact would occur on the field during one season of play. The second is that helmets that decrease acceleration decrease the risk of concussion. There are a number of concussion risk functions that have been developed to define probability of concussion as a function of linear head acceleration, angular head acceleration, or both. Debates over the mechanisms of brain injury and the ability of metrics that include linear or angular head acceleration to predict injury risk are long-standing.
Numerous studies have attempted to differentiate the effects of linear and angular head accelerations on brain injury and determine if one or the other is more likely to result in concussion. Current metrics for head injury safety standards use only linear head acceleration, and are based on human cadaver skull fracture and animal data. However, more recently it has been shown that the combination of linear and angular head acceleration is a good predictor of concussion, and that helmets reduce both linear and angular acceleration.
The Football STAR equation was developed to identify differences in the ability of football helmets to reduce concussion risk. The equation represents the predicted concussion incidence for a football player over one season. This predictive value is determined from laboratory tests with a helmeted headform to simulate head impacts at different locations and energy levels. Each laboratory condition is associated with the number of times that type of impact would occur over one season (exposure), and the probability that a concussion would occur due to the resultant head acceleration during each test (risk). In the Football STAR equation (Eq. 1), L represents the impact location of front, side, top, or back; H represents the drop height of 60, 48, 36, 24, or 12 in; E represents the exposure as a function of location and drop height, and R represents risk of concussion as a function of linear acceleration (a).
                              Football          ⁢                                          ⁢          STAR                =                              ∑                          L              =              1                        4                    ⁢                                    ∑                              H                =                1                            5                        ⁢                                          E                ⁡                                  (                                      L                    ,                    H                                    )                                            *                              R                ⁡                                  (                  a                  )                                                                                        (        1        )            